In regards to using your laptop to procrastinate you might find an extension such as StayFocusd useful, to restrict your access to specific sites for particular times/durations.
For the lists that you are making, I would recommend breaking them down further. Eg. instead of "revise bio module" and "revise chem module" you could have
Revise bio module
Complete 10 multiple choice questions
Spend 5 minutes on flashcards
Draw out labelled diagram for (process)
Revise chem module
Complete 5 short answer questions
Make post on atarnotes summarising (concept in module)
Watch video on (concept)
(not necessarily suggesting doing those things, but breaking tasks down into smaller chunks can help)
I'd also suggest you try and do some exercise, as this can help a lot with stress and being able to sleep later on.
If you find that you're feeling like this for a few weeks I would also highly encourage you to see a professional about it if you aren't already. From my experience, I found talking to a counsellor in year 12 to be very helpful.
If you want to rant, there are people here who will listen and do their best to help (me included) so try not to feel like that isn't an option. I'm glad you found ranting helpful this time
I have a tendency to catastrophise - I convinced myself during my first SAC that I would get a terrible ATAR, not get into any good courses etc. , and this is something it's very easy to do in year 12, especially if you have other things going on that make it more difficult to take care of your mental wellbeing. I want to remind you that these exams are NOT the sole contributor to your ATAR, and your ATAR does NOT determine your future. In my experience of uni, nobody cares whether you got into your course from transferring from a easier-admission course, your ATAR, a pathway, or anything else. Even if you don't follow the most ideal path to your future career, you can and will get there.
Even though it doesn't seem like it, this year is just a year. It doesn't define you or your academics. You and your circumstances will both change, and things will get better - eventually the trying pays off.